"As a lifelong beneficiary of the freedom to make jokes about religion, I do think that Boris Johnson's joke about wearers of the burqa resembling letterboxes is a pretty good one", Atkinson wrote in a letter to The Times newspaper, published on Friday.

The Tory peer said he had received a wave of abuse since speaking out against Mr Johnson. "On that basis, no apology is required".

Mr Johnson has also won the support of Tory former chief whip Andrew Mitchell, who said the Uxbridge MP had used "colourful" language but had not committed an offence.

He explained there was a complaints procedure within the Conservative Party and that the Party had a mechanism for dealing with these issues. His Brexiteer credentials were bolstered when he resigned as foreign secretary in July, accusing May of killing "the Brexit dream" with her plan to seek close economic ties with the bloc after Brexit next year.

The row has exposed bitter splits within the Tory Party, with many Remainer MPs using the controversy to stick the knife into Mr Johnson and say he is not fit to ever be party leader.